JPH0718099A - Prepreg excellent in tackiness and production thereof - Google Patents

Abstract

PURPOSE:To produce a prepreg improved in tackiness and drapeability without turbulence of a reinforcing fiber, by laminating 2 kinds of specific resin compsns. on a sheet-like reinforcement and pressing them. CONSTITUTION:(A) a resin compsn. comprising an epoxy resin and a curing agent as the main components and having a minimum viscosity of 0.5 to 150P as measured at a heat-up rate of 1.5 deg.C/min from room temp. and (B) a resin compsn. comprising an epoxy resin, a solid nitrile rubber and a curing agent as the main components and having a minimum viscosity of 200 to 3,000P as measured at a heat-up rate of 1.5 deg.C/min from room temp. are laminated on a film to obtain a composite film, which is then laminated on at least one surface of a sheet-like reinforcement, followed by pressing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prepreg excellent in tackiness and a method for producing the prepreg.

[0002]

2. Description of the Related Art A fiber reinforced composite material obtained from a prepreg composed of reinforcing fibers and a matrix resin is widely used as an advanced composite material mainly for aerospace and sports applications.

Such a fiber-reinforced composite material can be produced by stacking a plurality of prepregs, which are intermediate substrates, in the laminating step and then heating and curing the matrix resin in the molding step.

At this time, in order to obtain a void-free and dense molded product, it is necessary that the prepreg has appropriate tackiness and good handling property.

The prepreg used for producing the fiber reinforced composite material is at least one kind of reinforcing fiber such as glass fiber, carbon fiber or organic fiber impregnated with a thermosetting resin typified by epoxy resin as a matrix resin. Can be obtained by doing.

At this time, when a thermosetting resin such as an epoxy resin is used as a matrix, the thermosetting resin generally has an excellent adhesive property, so that the prepreg may be provided with the adhesive property. I can.

[0007]

However, when the thermoplastic resin is used alone as the matrix resin or when the epoxy resin is mixed with the thermoplastic resin, the adhesiveness of the matrix resin is significantly reduced. However, the tackiness of the obtained prepreg is significantly impaired.

Therefore, in order to increase the adhesiveness of the prepreg, a method of improving the adhesiveness of the matrix resin itself by blending an adhesive agent in the matrix resin can be considered.

However, according to this method, it is necessary to blend a large amount of the adhesive in the matrix resin in order to obtain the desired adhesiveness, which may lead to a marked deterioration in mechanical properties when the composite material is formed. is expected.

In order to reduce the weight of the composite material,
It is often required to increase the fiber content in the prepreg, but in this case, even if the adhesiveness of the matrix resin is excellent, the matrix resin content in the prepreg decreases, so the adhesiveness of the prepreg is reduced. However, there is a need for improvement.

Moreover, when the reinforcing fibers used are twisted, a restoring force acts on the reinforcing fibers in the untwisting direction. Therefore, after the matrix resin is impregnated into the reinforcing fibers, the matrix resin becomes a prepreg over time. The phenomenon of diving inside can be seen. Therefore, as a result of the amount of matrix resin on the surface portion of the prepreg being reduced, the adhesiveness of the prepreg is reduced even if the adhesiveness of the matrix resin is excellent. Further, the prepreg used for the honeycomb sandwich panel structure used from the viewpoint of weight saving of aircraft is required to have no porosity (void) in the molded plate. No pressure is applied to the prepreg in the upper and lower portions of the hexagonal cavity of the honeycomb core during molding, and as a result, inherent porosity is likely to occur in or between the prepreg laminated layers. In order to reduce the porosity between the laminated layers, it is necessary that the resin on the surface portion of the prepreg is sufficiently retained during molding, which means that the surface adhesiveness of the prepreg is excellent. Needless to say, it is important to improve the impregnation property of the prepreg in order to reduce the porosity in the laminated layer.

US Pat. No. 4,329,387 describes a prepreg having excellent tackiness obtained by sticking an adhesive resin on at least one surface of the prepreg. However, in this method, since prepreg-forming is performed in two steps, extra heat history is given to the prepreg, which impairs the drape property of the obtained prepreg and disturbs the fiber arrangement. It is easy to suffer from the drawback of being easy to lose.

Therefore, the present invention does not have the above-mentioned drawbacks and has excellent adhesiveness regardless of the type of matrix resin, the fiber content of the reinforcing fibers, and the presence or absence of twist of the reinforcing fibers, and the disturbance of the reinforcing fibers. It is an object of the present invention to provide a prepreg having a good drape property.

[0014]

The prepreg excellent in tackiness of the present invention has the following constitution in order to solve the above problems. That is, a prepreg composed of a sheet-shaped reinforcing material and two kinds of resin compositions A and B, and the resin composition A which is mainly impregnated in the sheet-shaped reinforcing material contains an epoxy resin and a curing agent as main components, and has a room temperature. The resin composition B having a minimum viscosity of 0.5 to 150 poise when measured at a temperature rising rate of 1.5 ° C./min from above, and mainly composed of an epoxy resin as a main component, is from room temperature. It is a prepreg excellent in tackiness, which has a minimum viscosity of 200 to 30,000 poise when measured at a temperature rising rate of 1.5 ° C./min.

Further, the method for producing a prepreg excellent in tackiness of the present invention has the following constitution in order to solve the above problems. That is, a layer composed of a resin composition A containing an epoxy resin and a curing agent as main components and having a minimum viscosity of 0.5 to 150 poise when measured at a temperature rising rate from room temperature of 1.5 ° C./min; Resin as the main component, from room temperature to 1.
The minimum viscosity is 200- when measured at a temperature rising rate of 5 ° C / min.
It is preferable that a layer of the resin composition A of a composite film obtained by laminating a layer of the resin composition B of 30,000 poise is laminated on at least one surface of the sheet-shaped reinforcing material, and then pressure is applied. This is a method for producing a prepreg having excellent adhesiveness.

The present invention will be described in detail below.

The reinforcing fiber which is a material of the sheet-like reinforcing material which is one of the constituent elements of the present invention is a fiber which is generally used as a high performance reinforcing fiber and has good heat resistance and tensile strength. For example, the reinforcing fibers include carbon fibers, graphite fibers, aramid fibers, silicon carbide fibers, alumina fibers and boron fibers. These reinforcing fibers are long fibers,
Either of the short fibers may be used. Further, one or more of these fibers may be mixed and used. Further, the reinforcing fiber is not limited in its shape and arrangement as long as it is in the form of a sheet having a certain width. For example, it may be used in the form of a unidirectionally aligned sheet, a random directional sheet, a mat, a woven fabric, a braid, etc. It is possible.

The resin composition A, which is one of the constituent elements of the present invention, includes thermosetting resins and thermoplastic resins, but these may be used as a mixture. The thermosetting resin that can be used in the present invention as the resin composition A is not particularly limited as long as it is a resin that is cured by heat or energy from the outside such as light or electron beam to at least partially form a three-dimensional cured product. Not done. Preferred thermosetting resins include epoxy resins and vinyl ester resins,
Generally, it is used in combination with a curing agent or a curing catalyst. Epoxy resins suitable for the present invention include amines,
An epoxy resin having a precursor having a compound having a carbon-carbon double bond as a phenol is preferred.

Specific examples of epoxy resins having amines as precursors include various isomers of tetraglycidyldiaminodiphenylmethane, triglycidyl-p-aminophenol, triglycidyl-m-aminophenol, and triglycidylaminocresol. To be

Examples of epoxy resins containing phenols as precursors include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, and resorcinol type epoxy resins. To be

Examples of the epoxy resin containing a compound having a carbon-carbon double bond as a precursor include alicyclic epoxy resins.

As the vinyl ester resin, epibis type, novolak type, urethane containing type, carboxy group containing type and the like are preferably used. Further, these epoxy resins and vinyl ester resins may be used alone,
You may mix and use it suitably.

The epoxy resin is preferably used in combination with an epoxy curing agent. As the epoxy curing agent, any compound having an active group capable of reacting with an epoxy group can be used. Specifically, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, dicyandiamide, boron trifluoride complex, polyphenol compound and the like can be used. For advanced applications such as aerospace, aromatic diamines such as
4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone or a mixture thereof,
For sports / leisure applications, dicyandiamide is preferably used. Further, imidazoles, urea compounds and the like can be used together with these curing agents as a curing accelerator.

The vinyl ester resin can be cured alone, but preferably an organic peroxide such as benzoyl peroxide or methyl ethyl ketone peroxide is used as a catalyst.

As the thermosetting resin which can be used in the present invention as the resin composition A, a maleimide resin, a resin having an acetylene terminal, a resin having a nadic acid terminal,
A resin having a cyanate ester terminal, a resin having a vinyl terminal, and a resin having an allyl terminal are preferably used. These may be appropriately mixed with an epoxy resin or another resin. Also, a reactive diluent may be used, or a modifier such as a thermoplastic resin or an elastomer may be mixed and used.

The maleimide resin is a compound containing an average of two or more maleimide groups at the terminals. This maleimide resin can be used alone, but when it is used in combination with a reactive diluent such as diallyl bisphenol A, it can be made a resin suitable for prepreg.
The resin having a cyanate ester terminal is preferably a cyanate ester compound of polyhydric phenol represented by bisphenol A. The cyanate ester resin can be made into a resin suitable for a prepreg, especially by combining with a bismaleimide resin.

As the resin composition A, a thermoplastic resin can be used in addition to the above-mentioned thermosetting resin. The preferred thermoplastic resin has a main chain selected from carbon-carbon bond, amide bond, imide bond, ester bond, ether bond, carbonate bond, urethane bond, urea bond, thioether bond, sulfone bond, imidazole bond and carbonyl bond. It is a thermoplastic resin having a bond.

In the present invention, the resin composition A has a minimum viscosity when measured from room temperature at a temperature rising rate of 1.5 ° C./min.
The porosity is 0.5 to 150 poise, preferably 3 to 100 poise. If the minimum viscosity is lower than 0.5 poise,
During molding, the resin flow becomes too large and a composite material having a predetermined resin content cannot be obtained. On the other hand, when the minimum viscosity is higher than 150 poise, the impregnating property into the reinforcing fiber is deteriorated.

In the present invention, the resin composition B has a minimum viscosity of 20 when measured from room temperature at a heating rate of 1.5 ° C./min.
It is set to 0 to 30,000 poise. When the minimum viscosity is lower than 200 poise, the fluidity of the resin composition B is large and the resin composition B easily penetrates into the sheet-like reinforcing material, and the change in prepreg adhesiveness with time increases. On the other hand, the minimum viscosity is 30,0
If it exceeds 00 poise, the tackiness decreases.

The resin composition B used in the present invention is for imparting tackiness to the prepreg, and a general diene-based tackiness agent can be used as the tackiness agent, but the heat resistance is improved. From the viewpoint of the above, an acrylic or silicone adhesive is preferably used. Further, since the silicone-based pressure-sensitive adhesive has water repellency, when this pressure-sensitive adhesive is blended, the water absorption of the composite material decreases, which is also preferable.

Examples of the diene-based adhesive include NBR, carboxyl-modified NBR, polyisoprene, SBR, carboxyl-modified SBR, SIS, SBS, SEBS, butyl rubber, polyisobutylene, and the like. From the point of compatibility with epoxy resin, NBR and carboxyl modified N
BR is preferable, and commercially available products thereof include Hiker CTBN1300 × 8 manufactured by BF Goodrich Chemical Co.,
Examples thereof include CTBN1300 × 13, CTBN1300 × 15, and Nippon Pole 1072 manufactured by Zeon Corporation.

As the acrylic adhesive, a polymer of an alkyl ester of acrylic acid or methacrylic acid is used. Long chain alkyl esters are suitable for developing tackiness in the polymer. The alkyl group preferably has 2 to 10 carbon atoms. This is because the glass transition temperature can be easily set to −50 ° C. or lower to exhibit sufficient tackiness.

As a matter of course, as long as the object of the present invention is achieved, it is perfectly possible to appropriately copolymerize the above-mentioned monomer having an alkyl group having carbon atoms with another acrylic monomer.

These acrylic pressure-sensitive adhesives can be modified with a carboxyl group, a hydroxyl group, a glycidyl group, an amino group or the like in order to improve the adhesive performance.

As the silicone-based pressure-sensitive adhesive, for example, a product such as "SH4280" sold by Toray Dow Corning Silicone Co., Ltd. may be applied to a prepreg and then heat-treated to obtain tackiness. I can.

As the resin composition B, the above-mentioned pressure-sensitive adhesive may be used alone, but in order to suppress deterioration of mechanical properties and heat resistance of the composite material, a thermosetting resin, and further a curing agent and a curing agent are used. It is preferable to blend and use a thermosetting resin in combination with a catalyst.

From the viewpoint of the adhesiveness of the prepreg, the coatability of the adhesive, and the maintenance of the mechanical properties of the composite material prepared from the prepreg, 50% by weight or more of a thermosetting resin, preferably 70% by weight.
It is preferable to use a thermosetting resin in an amount of ˜90% by weight in combination with an adhesive.

As the thermosetting resin, it is preferable to use the same type of resin as the resin used in the resin composition A from the viewpoint of maintaining mechanical properties when a composite material is used, and the above-mentioned epoxy resin and vinyl ester resin are used. To be

In the method for producing a prepreg of the present invention, an epoxy resin and a curing agent are used as main components, and the temperature is from room temperature to 1.5 ° C.
The minimum viscosity is 0.5 to 15 when measured at a heating rate of 1 / min.
A layer composed of a resin composition A having 0 poise, and a resin composition containing an epoxy resin as a main component and having a minimum viscosity of 200 to 30,000 poise when measured at a temperature rising rate of 1.5 ° C./min from room temperature. A composite film obtained by laminating layers of the product B is used. The resin cannot be impregnated in one step without using such a composite film.

In the present invention, the layer made of the resin composition A of the composite film is bonded to at least one surface of the sheet-like reinforcing material, and then heated and / or pressed. Unless such means are taken, it is difficult to obtain a prepreg having a desired structure.

In the prepreg of the present invention, from the viewpoint of imparting sufficient tackiness to the prepreg and preventing deterioration of mechanical properties such as interlaminar shear strength of the composite material, the resin composition B has a basis weight of 0.5 to 30 g / m ² , further 1.0
It is preferably in the range of ˜15 g / m ² . In order to obtain such a basis weight, first, the resin composition B may be coated on a release paper or a release film while being weighed, and the resin composition A may be further applied onto the release paper or the release film to form a composite film.

[0042] If the basis weight of the resin composition A and w _a g / m ^2, the preferred basis weight range, the basis weight of the sheet-like reinforcing material w _f g / m ^2, the basis weight of the resin composition B w _b g / M ² and the resin content in the prepreg are W _r (%), the value obtained by the following formula may be used as a guide.

W _a = {100 × w _b −W _r (w _b +
w _f )} / (W _r -100) Usually, the value of W _r is preferably 30 to 50%, more preferably 35 to 45%.

As described above, the composite film used in the present invention can be produced by first applying the resin composition B to a substrate such as release paper or a release film and then applying the resin composition A thereto. I can. As the method for providing the resin composition on the substrate, a solvent method in which the resin is dissolved in a solvent and then applied to the substrate, an emulsion method in which a polymer emulsion is applied, the resin is heated and melted, and the molten liquid is applied to a prepreg. Hot melt method and the like can be mentioned. In the case of an adhesive resin composition, since the viscosity of the adhesive used is high, the solvent method in which the adhesive is dissolved in a solvent to reduce the viscosity is preferably used.

On the other hand, in the case of the resin composition A, since the resin viscosity is low, the hot melt method which does not require volatilization of the solvent is preferable.

The prepreg excellent in tackiness of the present invention comprises a sheet-like reinforcing material, specifically, a reinforced fiber woven fabric or a unidirectionally aligned reinforcing fiber bundle, which is sandwiched between the above-mentioned composite films and roll-formed. It can be produced by a method of heating, pressurizing and impregnating as required.

Usually, in order to improve the tackiness of the prepreg by applying a pressure-sensitive adhesive to the surface of the prepreg, it is necessary to heat-impregnate the reinforcing fiber with the matrix resin and then further apply the pressure-sensitive adhesive. Will be needed. Therefore, the heat history applied to the prepreg becomes large, and the drape property of the obtained prepreg is impaired, or the fiber arrangement is likely to be disturbed.

On the other hand, according to the method of the present invention, it is possible to combine with the reinforcing fiber at once by using the composite film in which the resin composition B having adhesiveness and the resin composition A are previously applied in layers. Therefore, the heat history applied to the prepreg is reduced, and the above-mentioned defects are less likely to occur.

When a prepreg is produced using the method of the present invention, the matrix resin resin composition A is sufficiently impregnated into the reinforcing fibers, and the adhesive resin composition B is locally present on the prepreg surface. It needs to be localized. If the resin composition A is localized on the surface of the prepreg together with the resin composition B, impregnating property of the prepreg is deteriorated, and defects such as voids occur in the composite material obtained by using the prepreg. As a result, the mechanical properties of the composite material deteriorate. On the other hand, if the resin composition B enters the reinforcing fiber together with the resin composition A, it becomes impossible to impart sufficient tackiness to the prepreg.

In order to avoid such drawbacks and satisfy both the impregnating property and the tackiness of the prepreg, the reinforcing fiber should be treated without any consideration of the viscosity of the two resin compositions constituting the composite film. Therefore, it is necessary to optimize the pressure of the impregnating roll used when producing the prepreg. However, the viscosity of the resin in the resin layer A and the resin in the resin layer B, which have already been described above, are set to a specific range, and the object of the present invention can be easily achieved even in a pressure range usually used by increasing the viscosity difference. Is.

[0051]

【Example】

(Example 1) [Production of composite film] Nitrile rubber "Nipol10"
72 "(manufactured by Nippon Zeon Co., Ltd.) 30 parts by weight, epoxy resin" Ep828 "(manufactured by Yuka Shell Epoxy Co., Ltd.) 70
A 10% by weight solution of methyl ethyl ketone in which a curing agent dicyandiamide "DICY" and a curing aid 3,4-dichlorophenyl-1,1-dimethylurea "DCMU" were added to parts by weight of bar coater No. 22 (manufactured by Eto Kikai Co., Ltd.) was applied and dried at 50 ° C. for 10 minutes with a hot air dryer to obtain an adhesive resin film [resin layer B]. The resin areal weight at this time was 10 g / m ² .

Further, an epoxy resin composition [resin layer A] having the following composition was prepared in a kneader, then heated at 80 ° C. for a short time, and coated on the above adhesive resin film using a reverse coater, It was a composite resin film.
The basis weight of the obtained composite resin was 65 g / m ² .

<Epoxy resin> ELM434 (tetraglycidyl diaminodiphenylmethane) 40 parts by weight EPC830 (bisphenol F type epoxy) 20 parts by weight EPC152 (brominated bisphenol A type epoxy) 63 parts by weight EP828 (bisphenol A type epoxy) 127 parts by weight < Curing agent>4,4'-DDS(4,4'-diaminodiphenylsulfone) 80 parts by weight <Solid rubber> NIPOL1072 (carboxyl group terminated acrylonitrile butadiene rubber) 25 parts by weight (7.0% by weight) RDA manufactured by Rheometrics When the viscosity of the resin was measured using the -II type apparatus under the following conditions, the minimum viscosities of the resin layer B and the resin layer A were 5,000 poise and 90 poise, respectively.

(Viscosity measurement conditions) Operation mode: Dynamic mode Frequency 3.14 rad / sec Temperature rising rate: 1.5 ° C / min Plate configuration: Parallel plate (radius 25 mm) Gap 0.83 mm [Production of woven prepreg] This composite resin film is set in a prepreg machine and the carbon fiber woven fabric “CO7373
Resin impregnation was performed from both sides of "Z (manufactured by Toray Industries, Inc.)".
At this time, the impregnation temperature was 100 ° C., the impregnation pressure was 4 kgf / cm ² , and a fabric prepreg excellent in tackiness and drape having a resin content of 40% was obtained.

This prepreg was heated at 25 ° C. and a relative humidity of 50%.
After being left in the atmosphere for a certain period of time, the prepreg was attached to an aluminum plate with a double-sided tape and the peel strength was measured. As a result, it was compared with the prepreg in which the adhesive layer [resin layer B] was not applied. The peel strength after a certain period of time was greatly improved. The results are shown in Table 1.

[0056]

[Table 1] Next, one woven prepreg is placed on an aluminum plate coated with a silicone release agent, and the direction of the weaving yarn on it is ± 45 ° with respect to the weaving yarn of the prepreg woven fabric previously placed. A woven prepreg is then placed on top of the prepreg, and the size of the cell hole is ⅛ inch (about 3.2).
mm) with a thickness of 1/2 inch (about 12.7 mm), an aramid honeycomb body (a honeycomb body made of a material obtained by impregnating aramid paper with a heat-resistant phenolic resin) is placed, and two sheets of the above The prepreg was placed so that the direction of the weaving yarn was mirror-symmetrical to the fabric of the two prepregs initially placed with respect to the thickness center of the aramid honeycomb body, and the whole was packed with a fluororesin film.

The above-mentioned pack body was put into an autoclave, and the pressure inside the pack body was reduced while applying a pressure of 3 kgf / cm ² .
It was heated to 180 ° C. at a rate of 5 ° C./min and kept at that temperature for 2 hours to cure the epoxy resin of the woven fabric prepreg to form a skin and bond the skin and the honeycomb body.

When the cross section of the skin layer of the honeycomb sandwich panel thus obtained was observed with a microscope, no porosity (void) was observed.

Comparative Example 1 An epoxy resin composition having the same composition as in Example 1 was prepared in a kneader, heated at 80 ° C. for a short time, and coated on a release paper using a reverse coater to prepare a resin. It was a film. The basis weight of the obtained composite resin was 65 g / m ² .

Using this resin film, a prepreg was produced under the same conditions as in Example 1. Compared with the system of Example 1 using the composite resin film having the adhesive resin layer, the peel strength of the prepreg surface was extremely inferior.
The results are also shown in Table 1.

When the cross section of the skin layer of the honeycomb sandwich panel manufactured in the same manner as in Example 1 was observed with a microscope, a very large number of porosities (voids) were observed.

[0062]

EFFECTS OF THE INVENTION According to the present invention, since the desired tackiness can be imparted to the surface of the prepreg, the handling property of the prepreg can be remarkably improved, and the tackiness of the obtained prepreg does not easily change over time. Moreover, regardless of the type of the matrix resin, the fiber content of the reinforcing fibers, and the presence or absence of twists of the reinforcing fibers, it is possible to provide a prepreg having excellent tackiness, no disturbance of the reinforcing fibers, and good drapeability. Can be done.

Claims (4)

[Claims] 1. A sheet-shaped reinforcing material and two kinds of resin compositions A and B.
The resin composition A, which is mainly composed of an epoxy resin and a curing agent, is a prepreg consisting of a prepreg consisting of The minimum viscosity is 0.5 to 150 poise,
The resin composition B mainly arranged in the surface layer portion has an epoxy resin as a main component, and has a minimum viscosity of 200 to 30,000 poise when measured at a temperature rising rate of 1.5 ° C./min from room temperature. A characteristic prepreg with excellent adhesion. 2. The resin composition B comprises an epoxy resin, a solid nitrile rubber, and a curing agent.
Prepreg with excellent adhesiveness as described. 3. The resin composition B has a basis weight of 0.5 to 30 g / m.
^The prepreg having excellent adhesiveness according to claim 1 or ^2, which is ² . 4. An epoxy resin and a curing agent as main components,
A layer composed of a resin composition A having a minimum viscosity of 0.5 to 150 poise measured at a temperature rising rate of 1.5 ° C./min from room temperature, an epoxy resin as a main component, and a temperature of 1.5 ° C. from room temperature. /
The minimum viscosity is 200 to 30 when measured at a heating rate of minutes,
A composite film obtained by laminating a layer made of a resin composition B having a porosity of 000 poises is laminated with a layer made of the resin composition A toward at least one surface of a sheet-like reinforcing material, and then pressure is applied. A method for producing a prepreg having excellent adhesiveness.